Methods for Producing Non-Interfering Tooth Models

ABSTRACT

A method produces a physical dental arch model having at least two physical tooth models. The method includes detecting the interference between two physical tooth models. If interference is detected between the first physical tooth model and the second physical tooth model, the positions and orientations of at least one physical tooth model is modified to prevent interference between the first physical tooth model and the second physical tooth model.

CROSS-REFERENCES TO RELATED INVENTIONS

The present invention is also related to concurrently filed and commonlyassigned U.S. patent application Ser. No. titled “Storage system fordental devices” by Huafeng Wen and concurrently filed and commonlyassigned U.S. patent application Ser. No. titled “Intelligent trackingof dental devices” by Huafeng Wen.

The present invention is also related to commonly assigned U.S. patentapplication Ser. No. 11/013,152, titled “A base for physical dental archmodel” by Huafeng Wen, filed Dec. 14, 2004, commonly assigned U.S.patent application Ser. No. 11/012,924, titled “Accurately producing abase for physical dental arch model” by Huafeng Wen, filed Dec. 14,2004, commonly assigned U.S. patent application Ser. No. 11/013,145,titled “Fabricating a base compatible with physical dental tooth models”by Huafeng Wen, filed Dec. 14, 2004, commonly assigned U.S. patentapplication Ser. No. 11/013,156, titled “Producing non-interfering toothmodels on a base” by Huafeng Wen, filed Dec. 14, 2004, commonly assignedU.S. patent application Ser. No. 11/013,160, titled “System and methodsfor casting physical tooth model” by Huafeng Wen, filed Dec. 14, 2004,commonly assigned U.S. patent application Ser. No. 11/013,159, titled“Producing a base for accurately receiving dental tooth models” byHuafeng Wen, and filed Dec. 14, 2004, commonly assigned U.S. patentapplication Ser. No. 11/013,157, titled “Producing accurate base fordental arch model” by Huafeng Wen, filed Dec. 14, 2004.

The present invention is also related to commonly assigned U.S. patentapplication Ser. No. 10/979,823, titled “Method and apparatus formanufacturing and constructing a physical dental arch model” by HuafengWen, filed Nov. 2, 2004, U.S. patent application Ser. No. 10/979,497,titled “Method and apparatus for manufacturing and constructing a dentalaligner” by Huafeng Wen, filed Nov. 2, 2004, U.S. patent applicationSer. No. 10/979,504, titled “Producing an adjustable physical dentalarch model” by Huafeng Wen, filed Nov. 2, 2004, and U.S. patentapplication Ser. No. 10/979,824, titled “Producing a base for physicaldental arch model” by Huafeng Wen, filed Nov. 2, 2004. The disclosure ofthese related applications are incorporated herein by reference.

TECHNICAL FIELD

This application generally relates to the field of dental care, and moreparticularly to a system and a method for manufacturing and constructingphysical tooth models.

BACKGROUND

Orthodontics is the practice of manipulating a patient's teeth toprovide better function and appearance. In general, brackets are bondedto a patient's teeth and coupled together with an arched wire. Thecombination of the brackets and wire provide a force on the teethcausing them to move. Once the teeth have moved to a desired locationand are held in a place for a certain period of time, the body adaptsbone and tissue to maintain the teeth in the desired location. Tofurther assist in retaining the teeth in the desired location, a patientmay be fitted with a retainer.

To achieve tooth movement, orthodontists utilize their expertise tofirst determine a three-dimensional mental image of the patient'sphysical orthodontic structure and a three-dimensional mental image of adesired physical orthodontic structure for the patient, which may beassisted through the use of x-rays and/or models. Based on these mentalimages, the orthodontist further relies on his/her expertise to placethe brackets and/or bands on the teeth and to manually bend (i.e.,shape) wire, such that a force is asserted on the teeth to repositionthe teeth into the desired physical orthodontic structure. As the teethmove towards the desired location, the orthodontist makes continualjudgments as to the progress of the treatment, the next step in thetreatment (e.g., new bend in the wire, reposition or replace brackets,is head gear required, etc.), and the success of the previous step.

In general, the orthodontist makes manual adjustments to the wire and/orreplaces or repositions brackets based on his or her expert opinion.Unfortunately, in the oral environment, it is impossible for a humanbeing to accurately develop a visual three-dimensional image of anorthodontic structure due to the limitations of human sight and thephysical structure of a human mouth. In addition, it is humanlyimpossible to accurately estimate three-dimensional wire bends (with anaccuracy within a few degrees) and to manually apply such bends to awire. Further, it is humanly impossible to determine an ideal bracketlocation to achieve the desired orthodontic structure based on themental images. It is also extremely difficult to manually place bracketsin what is estimated to be the ideal location. Accordingly, orthodontictreatment is an iterative process requiring multiple wire changes, withthe process success and speed being very much dependent on theorthodontist's motor skills and diagnostic expertise. As a result ofmultiple wire changes, patient discomfort is increased as well as thecost. As one would expect, the quality of care varies greatly fromorthodontist to orthodontist as does the time to treat a patient.

As described, the practice of orthodontic is very much an art, relyingon the expert opinions and judgments of the orthodontist. In an effortto shift the practice of orthodontic from an art to a science, manyinnovations have been developed. For example, U.S. Pat. No. 5,518,397issued to Andreiko, et. al. provides a method of forming an orthodonticbrace. Such a method includes obtaining a model of the teeth of apatient's mouth and a prescription of desired positioning of such teeth.The contour of the teeth of the patient's mouth is determined, from themodel. Calculations of the contour and the desired positioning of thepatient's teeth are then made to determine the geometry (e.g., groovesor slots) to be provided. Custom brackets including a special geometryare then created for receiving an arch wire to form an orthodontic bracesystem. Such geometry is intended to provide for the disposition of thearched wire on the bracket in a progressive curvature in a horizontalplane and a substantially linear configuration in a vertical plane. Thegeometry of the brackets is altered, (e.g., by cutting grooves into thebrackets at individual positions and angles and with particular depth)in accordance with such calculations of the bracket geometry. In such asystem, the brackets are customized to provide three-dimensionalmovement of the teeth, once the wire, which has a two dimensional shape(i.e., linear shape in the vertical plane and curvature in thehorizontal plane), is applied to the brackets.

Other innovations relating to bracket and bracket placements have alsobeen patented. For example, such patent innovations are disclosed inU.S. Pat. No. 5,618,716 entitled “Orthodontic Bracket and Ligature” amethod of ligating arch wires to brackets, U.S. Pat. No. 5,011,405“Entitled Method for Determining Orthodontic Bracket Placement,” U.S.Pat. No. 5,395,238 entitled “Method of Forming Orthodontic Brace,” andU.S. Pat. No. 5,533,895 entitled “Orthodontic Appliance and GroupStandardize Brackets therefore and methods of making, assembling andusing appliance to straighten teeth”.

Kuroda et al. (1996) Am. J. Orthodontics 110:365-369 describes a methodfor laser scanning a plaster dental cast to produce a digital image ofthe cast. See also U.S. Pat. No. 5,605,459. U.S. Pat. Nos. 5,533,895;5,474,448; 5,454,717; 5,447,432; 5,431,562; 5,395,238; 5,368,478; and5,139,419, assigned to Ormco Corporation, describe methods formanipulating digital images of teeth for designing orthodonticappliances.

U.S. Pat. No. 5,011,405 describes a method for digitally imaging a toothand determining optimum bracket positioning for orthodontic treatment.Laser scanning of a molded tooth to produce a three-dimensional model isdescribed in U.S. Pat. No. 5,338,198. U.S. Pat. No. 5,452,219 describesa method for laser scanning a tooth model and milling a tooth mold.Digital computer manipulation of tooth contours is described in U.S.Pat. Nos. 5,607,305 and 5,587,912. Computerized digital imaging of thearch is described in U.S. Pat. Nos. 5,342,202 and 5,340,309.

Other patents of interest include U.S. Pat. Nos. 5,549,476; 5,382,164;5,273,429; 4,936,862; 3,860,803; 3,660,900; 5,645,421; 5,055,039;4,798,534; 4,856,991; 5,035,613; 5,059,118; 5,186,623; and 4,755,139.

The key to efficiency in treatment and maximum quality in results is arealistic simulation of the treatment process. Today's orthodontistshave the possibility of taking plaster models of the upper and lowerarch, cutting the model into single tooth models and sticking thesetooth models into a wax bed, lining them up in the desired position, theso-called set-up. This approach allows for reaching a perfect occlusionwithout any guessing. The next step is to bond a bracket at every toothmodel. This would tell the orthodontist the geometry of the wire to runthrough the bracket slots to receive exactly this result. The next stepinvolves the transfer of the bracket position to the originalmalocclusion model. To make sure that the brackets will be bonded atexactly this position at the real patient's teeth, small templates forevery tooth would have to be fabricated that fit over the bracket and arelevant part of the tooth and allow for reliable placement of thebracket on the patient's teeth. To increase efficiency of the bondingprocess, another option would be to place each single bracket onto amodel of the malocclusion and then fabricate one single transfer trayper arch that covers all brackets and relevant portions of every tooth.Using such a transfer tray guarantees a very quick and yet precisebonding using indirect bonding.

U.S. Pat. No. 5,431,562 to Andreiko et al. describes a computerized,appliance-driven approach to orthodontics. In this method, first certainshape information of teeth is acquired. A uniplanar target arcform iscalculated from the shape information. The shape of customized bracketslots, the bracket base, and the shape of the orthodontic archwire, arecalculated in accordance with a mathematically-derived target archform.The goal of the Andreiko et al. method is to give more predictability,standardization, and certainty to orthodontics by replacing the humanelement in orthodontic appliance design with a deterministic,mathematical computation of a target archform and appliance design.Hence the '562 patent teaches away from an interactive, computer-basedsystem in which the orthodontist remains fully involved in patientdiagnosis, appliance design, and treatment planning and monitoring.

More recently, Align Technologies began offering transparent, removablealigning devices as a new treatment modality in orthodontics. In thissystem, an impression model of the dentition of the patient is obtainedby the orthodontist and shipped to a remote appliance manufacturingcenter, where it is scanned with a CT scanner. A computer model of thedentition in a target situation is generated at the appliancemanufacturing center and made available for viewing to the orthodontistover the Internet. The orthodontist indicates changes they wish to maketo individual tooth positions. Later, another virtual model is providedover the Internet and the orthodontist reviews the revised model, andindicates any further changes. After several such iterations, the targetsituation is agreed upon. A series of removable aligning devices orshells are manufactured and delivered to the orthodontist. The shells,in theory, will move the patient's teeth to the desired or targetposition.

U.S. Pat. No. 6,699,037 Align Technologies describes an improved methodsand systems for repositioning teeth from an initial tooth arrangement toa final tooth arrangement. Repositioning is accomplished with a systemcomprising a series of appliances configured to receive the teeth in acavity and incrementally reposition individual teeth in a series of atleast three successive steps, usually including at least four successivesteps, often including at least ten steps, sometimes including at leasttwenty-five steps, and occasionally including forty or more steps. Mostoften, the methods and systems will reposition teeth in from ten totwenty-five successive steps, although complex cases involving many ofthe patient's teeth may take forty or more steps. The successive use ofa number of such appliances permits each appliance to be configured tomove individual teeth in small increments, typically less than 2 mm,preferably less than 1 mm, and more preferably less than 0.5 mm. Theselimits refer to the maximum linear translation of any point on a toothas a result of using a single appliance. The movements provided bysuccessive appliances, of course, will usually not be the same for anyparticular tooth. Thus, one point on a tooth may be moved by aparticular distance as a result of the use of one appliance andthereafter moved by a different distance and/or in a different directionby a later appliance.

The individual appliances will preferably include a polymeric shellhaving the teeth-receiving cavity formed therein, typically by moldingas described below. Each individual appliance will be configured so thatits tooth-receiving cavity has a geometry corresponding to anintermediate or end tooth arrangement intended for that appliance. Thatis, when an appliance is first worn by the patient, certain of the teethwill be misaligned relative to an undeformed geometry of the appliancecavity. The appliance, however, is sufficiently resilient to accommodateor conform to the misaligned teeth, and will apply sufficient resilientforce against such misaligned teeth in order to reposition the teeth tothe intermediate or end arrangement desired for that treatment step.

The fabrication of aligners by Align Technologies utilizes stereolithography process as disclosed in U.S. Pat. Nos. 6,471,511 and6,682,346. Several drawbacks exist however with the stereo lithographyprocess. The materials used by stereo lithography process may be toxicand harmful to human health. Stereo lithography process builds thealigner mold layer by layer causing the resulting aligners to have astairmaster like spacing between the layers and such spacing has atendency house germs and bacteria while it is worn by a patient.Furthermore, stereo lithography process used by Align Technology alsorequires a different aligner mold at each stage of the treatment, whichproduces waste and is environmental unfriendly.

The practice of orthodontics and other dental treatments includingpreparation of a denture can benefit from a physical dental arch modelthat is representative of the dentition and the alveolar ridge of apatient to be orthodontically treated. The physical dental arch model,also referred as a physical dental arch model, is often prepared basedon an impression model. The physical dental arch model is generallyprepared by cutting and arranging individual teeth on the alveolar ridgeof the impression model. With this physical dental arch model soprepared, not only is a final goal for the dental treatment made clear,but also the occlusal condition between the maxillary and the mandibulardentitions can be ascertained specifically.

Also, the patient when the physical dental arch model is presented canvisually ascertain the possible final result of orthodontic treatment heor she will receive and, therefore, the physical dental arch model is aconvenient tool in terms of psychological aspects of the patient.

Making a model for a whole or a large portion of an arch is moredifficult than making one tooth abutment for implant purposes. Singleteeth do not have concavities and complexities as in the inter-proximalareas of teeth in an arch. Some prior art making the physical dentalarch model is carried out manually, involving not only a substantialamount of labor required, but also a substantial amount of time. It isalso difficult to machine an accurate arch model because of the variouscomplex shapes and the complex features such as inter-proximal areas,wedges between teeth, etc. in an arch.

Another issue with the assembling of tooth models into a physical dentalarch model is that the adjacent tooth models can sometimes interferewith each other during an orthodontic treatment. The interference canoccur between the tooth portions of the two neighboring tooth modelswhen they are inserted into a base plate, or between the pins thatassist them to be mounted onto a base plate.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a method for producing aphysical dental arch model having at least two physical tooth models,comprising:

determining the positions and orientations of a first physical toothmodel;

determining the positions and orientations of a second physical toothmodel that is adjacent to the first physical tooth model;

detecting the interference between the first physical tooth model andthe second physical tooth model;

if interference is detected between the first physical tooth model andthe second physical tooth model, modifying the positions andorientations of at least one of the first physical tooth model and thesecond physical tooth model to prevent interference between the firstphysical tooth model and the second physical tooth model; and

fabricating the first physical tooth model and the second physical toothmodel in accordance with the modified positions and orientations of thefirst physical tooth model and/or the second physical tooth model.

In another aspect, the present invention relates to a method forproducing a physical dental arch model having at least two physicaltooth models, comprising:

producing a digital dental arch model that simulates the positions andorientations of a first physical tooth model and the positions andorientations of a second physical tooth model that is adjacent to thefirst physical tooth model;

detecting the interference between the first physical tooth model andthe second physical tooth model;

if interference is detected between the first physical tooth model andthe second physical tooth model, modifying the positions andorientations of at least one of the first physical tooth model and thesecond physical tooth model to produce a modified digital dental archmodel to prevent interference between the first physical tooth model andthe second physical tooth model; and

fabricating the first physical tooth model and the second physical toothmodel in accordance with the modified digital arch model.

In another aspect, the present invention relates to a method forproducing a physical dental arch model having at least two physicaltooth models, comprising:

producing a digital dental arch model that simulates the positions andorientations of a first physical tooth model and the positions andorientations of a second physical tooth model that is adjacent to thefirst physical tooth model, wherein the first physical tooth modelincludes a first feature affixed to the bottom portion of the firstphysical tooth model to allow the first physical tooth model to bemounted to a base and the second physical tooth model includes a secondfeature affixed to the bottom portion of the second physical tooth modelto allow the first physical tooth model to be mounted to the base.

detecting the interference between the first physical tooth model andthe second physical tooth model;

if interference is detected between the first physical tooth model andthe second physical tooth model, modifying the configurations of thefirst feature and/or the second feature to produce a modified digitaldental arch model to prevent interference between the first physicaltooth model and the second physical tooth model; and

fabricating the first physical tooth model having the first feature andthe second physical tooth model having the second feature in accordancewith the modified digital arch model.

Embodiments may include one or more of the following advantages. Anadvantage of the present invention is that adjacent physical toothmodels in a physical dental arch model can be assembled without theinterference between the tooth models. As a result, the positions andthe orientations of the tooth models can more accurately represent thedesired configurations in orthodontic treatments. The positions and theorientations of the tooth models can be iteratively modified until allinterference between adjacent tooth models in a arch model are removedbefore the tooth models are actually fabricated.

Another advantage of the present invention is that the physical toothmodels can be used to form different tooth arch models having differentteeth configurations. The pin configurations can be modified withoutchanging the tooth models themselves to be modified to preventinterference between adjacent tooth models at different steps of anorthodontic treatment. Moreover, the tooth models can be reused as toothpositions are changed during a treatment process. Much of the cost ofmaking multiple tooth arch models in orthodontic treatment are thereforeeliminated. The tooth models can have pins that assist their assemblingwith a base.

Another advantage of the present invention is that the same base cansupport different tooth arch models having different teethconfigurations. The base can include more than one sets of receivingfeatures that can receive tooth models at different positions. Thereusable base further reduces cost in the dental treatment of teethalignment. Furthermore, the receiving features can be modified toreceive tooth models having different pin configurations to avoidinterference between the adjacent tooth models in a tooth arch model aswell as interference during insertion of first feature to its matchingsecond feature.

The physical tooth models include features to allow them to be attached,plugged or locked to a base. The physical tooth models can bepre-fabricated having standard registration and attaching features forassembling. The physical tooth models can be automatically assembledonto a base by a robotic arm under computer control.

The physical dental arch model obtained by the disclosed system andmethods can be used for various dental applications such as dentalcrown, dental bridge, aligner fabrication, biometrics, and teethwhitening. The arch model can be assembled from segmented manufacturablecomponents that can be individually manufactured by automated, precisenumerical manufacturing techniques.

The physical tooth models in the physical dental arch model can beeasily separated, repaired or replaced, and reassembled after theassembly without the replacement of the whole arch model. Themanufacturable components can be attached to a base. The assembledphysical dental arch model specifically corresponds to the patient'sarch. There is no need for complex and costly mechanisms such asmicro-actuators for adjusting multiple degrees of freedom for each toothmodel. The described methods and system is simple to make and easy touse.

The details of one or more embodiments are set forth in the accompanyingdrawing and in the description below. Other features, objects, andadvantages of the invention will become apparent from the descriptionand drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention:

FIG. 1 is a flow chart for producing a physical dental arch model inaccordance with the present invention.

FIG. 2 illustrates a tooth model and a base respectively comprisingcomplimentary features for assembling the tooth model with the base.

FIG. 3 illustrates fixing a stud to a tooth model comprising a femalesocket to produce a tooth model having a protruded stud.

FIG. 4 illustrate a tooth model comprising two pins that allow the toothmodel to be plugged into two corresponding holes in a base.

FIG. 5 illustrate a tooth model comprising a protruded pin that allowsthe tooth model to be plugged into a hole in a base.

FIG. 6 illustrates cone shaped studs protruded out of the bottom of atooth model.

FIG. 7 illustrates exemplified shapes for the studs at the bottom of atooth model.

FIG. 8A illustrates an example of a base comprising a plurality offemale sockets for receiving a plurality of tooth models for forming aphysical dental arch model.

FIG. 8B illustrates another example of a base comprising a plurality offemale sockets for receiving a plurality of tooth models for forming aphysical dental arch model.

FIG. 9 illustrates a tooth model that can be assembled to the base inFIGS. 8A and 8B.

FIG. 10 illustrates an example in which the pins at the bottom portionsof two adjacent tooth models interfere with each other.

FIG. 11 illustrates an example in which two adjacent tooth modelsmounted on a base interfere with each other at the tooth portions of thetooth models.

FIG. 12 illustrates a tooth model having pin configurations that preventthe tooth models from interfering with each other.

FIG. 13( a) is a front view of two tooth models having pinconfigurations of FIG. 12.

FIG. 13( b) is a perspective bottom view of two tooth models having pinconfigurations of FIG. 12.

FIG. 14 illustrates a mechanism for fixing tooth models to a base usingremovable pins.

FIG. 15 illustrates a mechanism for fixing tooth models to a base usingspring-loaded pins to prevent interference between tooth models.

FIG. 16 illustrates a variation of the mechanism of FIG. 15 to preventinterference between tooth models.

FIG. 17 illustrates another variation of the mechanism of FIG. 15 toprevent interference between tooth models.

DESCRIPTION OF INVENTION

Major operations in producing a physical dental arch model areillustrated in FIG. 1. The process generally includes the followingsteps. First individual tooth model is created in step 110. Anindividual tooth model is a physical model that can be part of aphysical tooth arch model, which can be used in various dentalapplications. Registration features are next added to the individualtooth model to allow them to be attached to each other or a base in step120. A base is designed for receiving the tooth model in step 130. Thetooth model positions in a tooth arch model are next determined in step140. The interference between all adjacent tooth models are determinedin step 145. If there is no interference is detected, the process skipsto step 160. If interference is detected, the pin configurations affixedto the tooth models are modified in step 150 to prevent interferencebetween adjacent tooth models when they are mounted on the base. A baseis fabricated in step 160. The base includes features for receiving theindividual tooth model having the selected pin configurations. The toothmodels are finally attached to the base at the predetermined positionsusing the pre-designed features in step 170.

Details of process in FIG. 1 are now described. Individual tooth modelcan be obtained in step 110 in a number of different methods. The toothmodel can be created by casting. A negative impression is first madefrom a patient's arch using for example PVS. A positive of the patient'sarch is next made by pouring a casting material into the negativeimpression. After the material is dried, the mould is then taken outwith the help of the impression knife. A positive of the arch is thusobtained.

In an alternative approach, the negative impression of the patient'sarch is placed in a specially designed container. A casting material isthen poured into the container over the impression to create a model. Alid is subsequently placed over the container. The container is openedand the mould can be removed after the specified time.

Examples of casting materials include auto polymerizing acrylic resin,thermoplastic resin, light-polymerized acrylic resins, polymerizingsilicone, polyether, plaster, epoxies, or a mixture of materials. Thecasting material is selected based on the uses of the cast. The materialshould be easy for cutting to obtain individual tooth model.Additionally, the material needs to be strong enough for the tooth modelto take the pressure in pressure form for producing a dental aligner.Details of making a dental aligner are disclosed in commonly assignedand above referenced U.S. patent application Ser. No. titled “Method andapparatus for manufacturing and constructing a dental aligner” byHuafeng Wen, filed Nov. 2, 2004, the content of which is incorporatedherein by reference.

Features that can allow tooth models to be attached to a base (step 120)can be added to the casting material in the casting process.Registration points or pins can be added to each tooth before thecasting material is dried. Optionally, universal joints can be insertedat the top of the casting chamber using specially designed lids, whichwould hang the universal joints directly into the casting area for eachtooth.

Still in step 110, individual tooth models are next cut from the archpositive. One requirement for cutting is to obtain individual teeth insuch a manner that they can be joined again to form a tooth arch. Theseparation of individual teeth from the mould can be achieved using anumber of different cutting methods including laser cutting andmechanical sawing.

Separating the positive mould of the arch into tooth models may resultin the loss of the relative 3D coordinates of the individual toothmodels in an arch. Several methods are provided in step 120 for findingrelative position of the tooth models. In one embodiment, uniqueregistration features are added to each pair of tooth models before thepositive arch mould is separated. The separated tooth models can beassembled to form a physical dental arch model by matching tooth modelshaving the same unique registration marks.

The positive arch mould can also be digitized by a three-dimensionalscanning using a technique such as laser scanning, optical scanning,destructive scanning, CT scanning and Sound Wave Scanning. A digitaldental arch model is therefore obtained. The digital dental arch modelis subsequently smoothened and segmented. Each segment can be physicallyfabricated by CNC based manufacturing to obtain individual tooth models.The digital dental arch model tracks and stores the positions of theindividual tooth models. Unique registration marks can be added to thedigital tooth models that can be made into a physical feature in CNCbase manufacturing.

Examples of CNC based manufacturing include CNC based milling,Stereolithography, Laminated Object Manufacturing, Selective LaserSintering, Fused Deposition Modeling, Solid Ground Curing, 3D ink jetprinting. Details of fabricating tooth models are disclosed in commonlyassigned and above referenced U.S. patent application Ser. No. titled“Method and apparatus for manufacturing and constructing a physicaldental arch mode” by Huafeng Wen, filed Nov. 2, 2004, the content ofwhich is incorporated herein by reference.

In another embodiment, the separated tooth models are assembled bygeometry matching. The intact positive arch impression is first scannedto obtain a 3D digital dental arch model. Individual teeth are thenscanned to obtain digital tooth models for individual teeth. The digitaltooth models can be matched using rigid body transformations to match adigital dental arch model. Due to complex shape of the arch,inter-proximal areas, root of the teeth and gingival areas may beignored in the geometry match. High precision is required for matchingfeatures such as cusps, points, crevasses, the front and back faces ofthe teeth. Each tooth is sequentially matched to result in rigid bodytransformations corresponding to the tooth positions that canreconstruct an arch.

In another embodiment, the separated tooth models are assembled andregistered with the assistance of a 3D point picking devices. Thecoordinates of the tooth models are picked up by 3D point pickingdevices such as stylus or Microscribe devices before separation. Uniqueregistration marks can be added on each tooth model in an arch beforeseparation. The tooth models and the registration marks can be labeledby unique IDs. The tooth arch can later be assembled by identifyingtooth models having the same registration marks as were picked from theJaw. 3D point picking devices can be used to pick the same points againfor each tooth model to confirm the tooth coordinates.

The base is designed in step 130 to receive the tooth models. The baseand tooth models include complimentary features to allow them to beassembled together. The tooth model has a protruding structure attachedto it. The features at the base and tooth models can also include aregistration slot, a notch, a protrusion, a hole, an interlockingmechanism, and a jig. The protruding structure can be obtained duringthe casting process or be created after casting by using a CNC machineon each tooth. The positions of the receiving features in the base isdetermined by either the initial positions of the teeth in an arch orthe desired teeth positions during a treatment process (step 140).

In step 145, all pairs of adjacent tooth models in the digital dentalarch model are examined to detect the existence of any interference orcollision. The interference or collision can exist between the adjacenttooth models the features affixed to the bottom of the tooth models. Ifinterference is detected between a pair of adjacent tooth models, theconfigurations of the features can be modified to avoid suchinterference. In particular, the lengths and orientations of the pinsaffixed to the bottom of the tooth models can be adjusted to avoidinterference. The tooth models can be affixed with one or more pins attheir bottom portions for the tooth models to be inserted into the base.The two adjacent tooth models can interfere with each other when theyare inserted into a base. The pin configurations are selected in step150 to prevent interference between adjacent tooth models.

In FIG. 15 for example, the two pins 1540, 1550 attached to the bottomof the tooth portion may originally have equal lengths. The lengths ofthe two pins 1540, 1550 can be adjusted to be different to avoidinterference. Furthermore, the tilt angles of pins 1540, 1550 can beadjusted also to prevent interference between tooth models. As shown inthe steps 145, 150 and 160, the adjustment of the features affixed tothe tooth models and the positions and/or orientation of the toothmodels can be an iterative process.

Two adjacent tooth models 1010 and 1020 are shown in FIG. 10. The toothmodels 1010, 1020 are respectively affixed with pins 1015 and pins 1025.The orthodontic treatment requires the two adjacent tooth models 1010and 1020 to be tilted away from each other in a tooth arch model. As aresult, the pins 1015 and the pins 1025 interfere with or collide intoeach other. In another example, as shown in FIG. 11, two adjacent toothmodels 1110 and 1120 are required to tilt toward each other by theorthodontic treatment. The tooth models 1110 and 1120 are affixed withpins having equal pin lengths. The tooth models 1110 and 1120 cancollide into each other when they are inserted into a base 1130 becausethe insertion angles required by the long insertion pins.

In accordance with the present invention, the interference betweenadjacent tooth models mounted on an arch can be resolved by properlydesigning and selecting configurations of the pins affixed to the bottomportion of the tooth models. FIG. 12 illustrates a tooth model 1200having two pins 1210 and 1220 affixed to the bottom portion. To preventinterference of the tooth model 1200 with its neighboring tooth models,the pins 1210 and 1220 are designed to have different lengths.

FIGS. 13( a) and 13(b) show detailed perspective views how two toothmodels having the pin configurations shown in FIG. 12 can avoidinterfering with each other. FIG. 13( a) shows the front perspectiveview of two tooth models 1310 and 1320 each of which is respectivelyaffixed pins 1315 and 1325. The pins 1315 and pins 1325 are configuredto have different lengths so that the pins do not run into each otherwhen they are inserted into a base (not shown in FIG. 13( a) forclarity). The avoidance of interference between the tooth models 1310and 1320 is also illustrated in a perspective bottom view in FIG. 13(b).

The pin configurations for tooth models can be selected by differentmethods. In one embodiment, a digital dental arch model that representsthe physical tooth model is first produced or received. The digitaldental arch model defines the positions and orientations of the twoadjacent physical tooth models in the physical dental arch modelaccording to the requirement of the orthodontic treatment. The positionsof the physical tooth models including the pins are simulated to examinethe interference between two adjacent physical tooth models mounted onthe base. The pin configurations are adjusted to avoid any interferencethat might occur in the simulation. The pin configurations can includepins lengths, pin positions at the underside of the tooth models, andthe number of pins for each tooth model.

The tooth models affixed with pins having the selected pinconfigurations can fabricated by Computer Numerical Control (CNC) basedmanufacturing in response to the digital dental arch model. At differentsteps of an orthodontic treatment, the tooth portions of the toothmodels can remain the same while the pins affixed to the tooth portionbeing adjusted depending on the relative orientation of positionsbetween adjacent tooth models. Furthermore, the base can includedifferent socket configurations that is adapted to receive compatiblepin configurations selected for different steps of the orthodontictreatment. The physical tooth models and their pin configurations can belabeled by a predetermined sequence to define the positions of thephysical tooth models on the base for each step of the orthodontictreatment.

An advantage of the present invention is that the different pinconfigurations allow longer pins affixed to the tooth models, whichresults in more stable physical tooth arch model. Another advantage isthat the tooth portion of the tooth models can be reused for differentsteps of an orthodontic treatment. Modular sockets can be prepared onthe underside of the tooth models. Pins of different lengths can beplugged into the sockets to prevent interference between adjacent toothmodels.

Before casting the arch from the impression, the base plate is takenthrough a CNC process to create the female structures for eachindividual tooth (step 160). Then the base is placed over the castingcontainer in which the impression is already present and the containeris filled with epoxy. The epoxy gets filled up in the female structuresand the resulting mould has the male studs present with each tooth modelthat can be separated afterwards. FIG. 2 shows a tooth model 210 withmale stud 220 after mould separation. The base 230 comprises a femalefeature 240 that can receive the male stud 220 when the tooth model 210is assembled to the base 230.

Alternatively, as shown in FIG. 3, a tooth model 310 includes a femalesocket 315 that can be drilled by CNC based machining after casting andseparation. A male stud 320 that fits the female socket 315 can beattached to the tooth model 310 by for example, screwing, glueapplication, etc. The resulted tooth model 330 includes male stud 310that allows it to be attached to the base.

Male protrusion features over the tooth model can exist in a number ofarrangements. FIG. 4 shows a tooth model 410 having two pins 415sticking out and a base 420 having registration slots 425 adapted toreceive the two pins 415 to allow the tooth model 410 to be attached tothe base 420. FIG. 5 shows a tooth model 510 having one pins 515protruding out and a base 520 having a hole 525 adapted to receive thepin 515 to allow the tooth model 510 to be attached to the base 520. Ingeneral, the tooth model can include two or more pins wherein the basewill have complementary number of holes at the corresponding locationsfor each tooth model. The tooth model 610 can also include cone shapedstuds 620 as shown in FIG. 6. The studs can also take a combination ofconfigurations described above.

As shown FIG. 7, the studs protruding our of the tooth model 710 cantake different shapes 720 such as oval, rectangle, square, triangle,circle, semi-circle, each of which correspond to slots on the basehaving identical shapes that can be drilled using the CNC basedmachining. The asymmetrically shaped studs can help to define a uniqueorientation for the tooth model on the base.

FIG. 8A shows a base 800 having a plurality of sockets 810 and 820 forreceiving the studs of a plurality of tooth models. The positions of thesockets 810,820 are determined by either her initial teeth positions ina patient's arch or the teeth positions during the orthodontic treatmentprocess. The base 800 can be in the form of a plate as shown in FIG. 8,comprising a plurality of pairs of sockets 810,820. Each pair of sockets810,820 is adapted to receive two pins associated with a physical toothmodel. Each pair of sockets includes a socket 810 on the inside of thetooth arch model and a socket 820 on the outside of the tooth archmodel.

Another of a base 850 is shown in FIG. 8B. A plurality of pairs offemale sockets 860, 870 are provided in the base 850. Each pair of thesockets 860, 870 is formed in a surface 880 and is adapted to receive aphysical tooth model 890. The bottom portion of the physical tooth model890 includes a surface 895. The surface 895 comes to contact with thesurface 880 when the physical tooth model 890 is inserted into the base850, which assures the stability of the physical tooth model 890 overthe base 850.

A tooth model 900 compatible with the base 800 is shown in FIG. 9. Thetooth model 900 includes two pins 910 connected to its bottom portion.The two pins 910 can be plugged into a pair of sockets 810 and 820 onthe base 800. Thus each pair of sockets 810 and 820 uniquely defines thepositions of a tooth model. The orientation of the tooth model is alsouniquely defined if the two pins are labeled as inside and outside, orthe sockets and the pins are made asymmetric inside and outside. Ingeneral, each tooth model may include correspond to one or a pluralityof studs that are to be plugged into the corresponding number ofsockets. The male studs and the sockets may also take different shapesas described above.

In another embodiment, the disclosed methods and system can includeteeth duplicate with removable or retractable pins, as shown in FIGS. 14and 15. A tooth model 1450 is placed on a flat surface 1460 in a recesscreated in the base 1440. The base 1440 include through holes 1425 and1435. The tooth model 1450 includes at the bottom portion drilled holes1420 and 1430 that are in registration and alignment with the throughholes 1425 and 1435. Pins 1410 can then be inserted along directions1412, 1413 into the through holes 1425 and 1435 in the base and thenholes 1420 and 1430 in the base to affix the tooth models 1450 into thebase 1440.

In another embodiment, the features affixed to the bottom portion of thephysical tooth model can include a spring loaded pin mechanism. As shownin FIG. 15, the tooth model 1510 includes holes 1520. Pins 1540 and 1550can be inserted into the holes 1520 in spring load mechanisms 1530,1540. The pins 1540 are retractable with compressed springs to avoidinterference during insertion or after the installation of the toothmodel over the base. After the tooth models are properly mounted andfixed, the pins 1540 can extend to their normal positions to maximizeposition and angle control.

The overall pin lengths can be cut to the correct lengths to becompatible with the spring load mechanisms to prevent interferencebetween tooth models. FIG. 16 shows a variation of the retractable pinmechanism. The tooth model 1610 includes holes 1620. Pins 1640 and 1650can be inserted into the holes 1620 in spring load mechanisms 1630,1640. The retractable pins 1640 are of different lengths to avoidinterference during insertion or after the installation of the toothmodel over the base. After the tooth models are properly mounted andfixed, the pins 1640 can extend to their normal positions to maximizeposition and angle control.

The retractable pins can also be tilted to the bottom portion of thephysical tooth model to prevent interference between tooth models. FIG.17 shows a variation of the retractable pin mechanism. The tooth model1710 includes holes 1720. Pins 1740 and 1750 can be inserted into theholes 1720 in spring load mechanisms 1730, 1740. The retractable pins1740 are tilted relative to the bottom of the tooth model 1710 to avoidinterference during insertion or after the installation of the toothmodel over the base. After the tooth models are properly mounted andfixed, the pins 1740 can extend to their normal positions to maximizeposition and angle control.

The described methods are also applicable to prevent tooth modelinterference in precision mount of tooth models in casting chambers. Insuch cases, the shape and the height of the tooth models can be modifiedto avoid interference of teeth during insertion or at the correspondingtreatment positions.

A tooth arch model is obtained after the tooth models are assembled tothe base 800 (step 170). The base 800 can comprise a plurality ofconfigurations in the female sockets 810. Each of the configurations isadapted to receive the same physical tooth models to form a differentarrangement of at least a portion of a tooth arch model.

The base 800 can be fabricated by a system that includes a computerdevice adapted to store digital tooth models representing the physicaltooth models. As described above, the digital tooth model can beobtained by various scanning techniques. A computer processor can thengenerate a digital base model compatible with the digital tooth models.An apparatus fabricates the base using CNC based manufacturing inaccordance with the digital base model. The base fabricated is adaptedto receive the physical tooth models.

The physical tooth models can be labeled by a predetermined sequencethat define the positions of the physical tooth models on the base 800.The labels can include a barcode, a printed symbol, hand-written symbol,a Radio Frequency Identification (RFID). The female sockets 810 can alsobe labeled by the parallel sequence for the physical tooth models.

In one embodiment, tooth models can be separated and repaired after thebase. The tooth models can be removed, repaired or replaced, andre-assembled without the replacement of the whole arch model.

Common materials for the tooth models include polymers, urethane, epoxy,plastics, plaster, stone, clay, acrylic, metals, wood, paper, ceramics,and porcelain. The base can comprise a material such as polymers,urethane, epoxy, plastics, plaster, stone, clay, acrylic, metals, wood,paper, ceramics, porcelain, glass, and concrete.

The arch model can be used in different dental applications such asdental crown, dental bridge, aligner fabrication, biometrics, and teethwhitening. For aligner fabrication, for example, each stage of the teethtreatment may correspond a unique physical dental arch model. Alignerscan be fabricated using different physical dental arch models one at atime as the teeth movement progresses during the treatment. At eachstage of the treatment, the desirable teeth positions for the next stageare calculated. A physical dental arch model having modified teethpositions is fabricated using the process described above. A new aligneris made using the new physical dental arch model.

In accordance with the present invention, each base is specific to anarch configuration. There is no need for complex and costly mechanismssuch as micro-actuators for adjusting multiple degrees of freedom foreach tooth model. The described methods and system is simple to make andeasy to use.

The described methods and system are also economic. Different stages ofthe arch model can share the same tooth models. The positions for thetooth models at each stage of the orthodontic treatment can be modeledusing orthodontic treatment software. Each stage of the arch model mayuse a separate base. Or alternatively, one base can be used in aplurality of stages of the arch models. The base may include a pluralityof sets of receptive positions for the tooth models. Each setcorresponds to one treatment stage. The tooth models can be reusedthrough the treatment process. Much of the cost of making multiple tootharch models in orthodontic treatment are therefore eliminated.

Although specific embodiments of the present invention have beenillustrated in the accompanying drawings and described in the foregoingdetailed description, it will be understood that the invention is notlimited to the particular embodiments described herein, but is capableof numerous rearrangements, modifications, and substitutions withoutdeparting from the scope of the invention. The following claims areintended to encompass all such modifications.

1. A method for producing a physical dental arch model having at leasttwo physical tooth models, comprising: determining the positions andorientations of a first physical tooth model; determining the positionsand orientations of a second physical tooth model that is adjacent tothe first physical tooth model; detecting the interference between thefirst physical tooth model and the second physical tooth model; ifinterference is detected between the first physical tooth model and thesecond physical tooth model, modifying the positions and orientations ofat least one of the first physical tooth model and the second physicaltooth model to prevent interference between the first physical toothmodel and the second physical tooth model; and fabricating the firstphysical tooth model and the second physical tooth model in accordancewith the modified positions and orientations of the first physical toothmodel and/or the second physical tooth model.
 2. The method of claim 1,wherein the first physical tooth model includes a first feature affixedto the bottom portion of the first physical tooth model to allow thefirst physical tooth model to be mounted to a base and the secondphysical tooth model includes a second feature affixed to the bottomportion of the second physical tooth model to allow the first physicaltooth model to be mounted to the base.
 3. The method of claim 2, furthercomprising modifying the first feature or the second feature to preventinterference between the first physical tooth model and the secondphysical tooth model.
 4. The method of claim 2, wherein the firstfeature comprises one or more of a pin, a registration slot, a socket, anotch, a protrusion, a hole, an interlocking mechanism, a jig, and apluggable or attachable feature.
 5. The method of claim 2, wherein thefirst feature comprises at least one pin affixed to the bottom portionof the first tooth model and the base comprises at least one socketconfigured to receive the pin.
 6. The method of claim 5, furthercomprising modifying the length and/or the orientations of the pinrelative to the bottom portion of the pin to prevent interferencebetween the first physical tooth model and the second physical toothmodel.
 7. The method of claim 2, further comprising fabricating thefirst physical tooth model having the first feature; and fabricating thesecond physical tooth model having the second feature.
 8. The method ofclaim 2, wherein the first feature affixed to the bottom portion of thefirst physical tooth model includes a spring loaded pin mechanism. 9.The method of claim 8, wherein the first feature affixed to the bottomportion of the first physical tooth model having the spring loaded pinmechanism comprises two pins of different lengths or pins tilted to thebottom portion of the first physical tooth model.
 10. A method forproducing a physical dental arch model having at least two physicaltooth models, comprising: producing a digital dental arch model thatsimulates the positions and orientations of a first physical tooth modeland the positions and orientations of a second physical tooth model thatis adjacent to the first physical tooth model; detecting theinterference between the first physical tooth model and the secondphysical tooth model; if interference is detected between the firstphysical tooth model and the second physical tooth model, modifying thepositions and orientations of at least one of the first physical toothmodel and the second physical tooth model to produce a modified digitaldental arch model to prevent interference between the first physicaltooth model and the second physical tooth model; and fabricating thefirst physical tooth model and the second physical tooth model inaccordance with the modified digital arch model.
 11. The method of claim10, wherein the first physical tooth model includes a first featureaffixed to the bottom portion of the first physical tooth model to allowthe first physical tooth model to be mounted to a base and the secondphysical tooth model includes a second feature affixed to the bottomportion of the second physical tooth model to allow the first physicaltooth model to be mounted to the base.
 12. The method of claim 11,further comprising modifying the first feature or the second feature toproduce the modified digital dental arch model to prevent interferencebetween the first physical tooth model and the second physical toothmodel.
 13. The method of claim 11, wherein the first feature comprisesone or more of a pin, a registration slot, a socket, a notch, aprotrusion, a hole, an interlocking mechanism, a jig, and a pluggable orattachable feature.
 14. The method of claim 11, wherein the firstfeature comprises at least one pin affixed to the bottom portion of thefirst tooth model and the base comprises at least one socket configuredto receive the pin.
 15. The method of claim 14, further comprisingmodifying the length and/or the orientations of the pin relative to thebottom portion of the pin to prevent interference between the firstphysical tooth model and the second physical tooth model.
 16. The methodof claim 11, wherein the first feature affixed to the bottom portion ofthe first physical tooth model includes a spring loaded pin mechanism.17. The method of claim 11, further comprising fabricating the firstphysical tooth model having the first feature; fabricating the secondphysical tooth model having the second feature; and fabricating the basethat is configured to receive with the first physical tooth model andthe second physical tooth model.
 18. A method for producing a physicaldental arch model having at least two physical tooth models, comprising:producing a digital dental arch model that simulates the positions andorientations of a first physical tooth model and the positions andorientations of a second physical tooth model that is adjacent to thefirst physical tooth model, wherein the first physical tooth modelincludes a first feature affixed to the bottom portion of the firstphysical tooth model to allow the first physical tooth model to bemounted to a base and the second physical tooth model includes a secondfeature affixed to the bottom portion of the second physical tooth modelto allow the first physical tooth model to be mounted to the base.detecting the interference between the first physical tooth model andthe second physical tooth model; if interference is detected between thefirst physical tooth model and the second physical tooth model,modifying the configurations of the first feature and/or the secondfeature to produce a modified digital dental arch model to preventinterference between the first physical tooth model and the secondphysical tooth model; and fabricating the first physical tooth modelhaving the first feature and the second physical tooth model having thesecond feature in accordance with the modified digital arch model. 19.The method of claim 18, wherein the first feature comprises at least onepin affixed to the bottom portion of the first tooth model and the basecomprises at least one socket configured to receive the pin.
 20. Themethod of claim 19, further comprising modifying the length and/or theorientations of the pin to prevent interference between the firstphysical tooth model and the second physical tooth model.